Posterior Force Research Articles

Line Hops and Side Hold Rotation Tests Load Both Anterior and Posterior Shoulder: A Biomechanical Study.

BackgroundClinical tests should replicate the stressful positions encountered during sport participation. Evaluating the kinetic and electromyographical demands of clinical tests enables clinicians to choose appropriate tests for specific sports.PurposeTo describe the shoulder forces and muscle activation levels during closed chain functional tests of Line Hops (LH) and Side Hold Rotation (SHR).Study DesignDescriptive biomechanical studyMethodsTen asymptomatic participants were examined in a university laboratory. Two functional tests were evaluated using three-dimensional video analysis and electromyography to measure shoulder forces, moments, and muscular activity levels.ResultsSHR produced a peak average posterior translation force of 4.84 N/kg (CI95 4.32-5.36N/kg) and a peak average anterior translational force of 1.57 N/kg (CI95 1.10-2.01N/kg). High levels of serratus anterior (98% maximum voluntary isometric contraction (MVIC) and infraspinatus (52 %MVIC) were recorded during SHR. LH produced a posterior translational force of 4.25 N/kg (CI95 3.44–5.06N/kg). High levels of serratus anterior (105 %MVIC) and infraspinatus (87 %MVIC) were recorded during the push off phase of this activity.ConclusionsLH and SHR placed large posterior translational forces that approached half of a person’s bodyweight on shoulder structures. SHR produced an anterior translation force at extremes of horizontal abduction placing approximately 18% of bodyweight on shoulder structures. The LH test required the serratus anterior to provide power to push the upper torso of the ground while both the serratus and the infraspinatus provides scapular and humeral stability, respectively.Level of Evidence4: Case series

Potential Instability and Malfunction of Knee Joints with Vastus Medialis Impairment after Total Knee Arthroplasty

Four pairs of fresh-frozen cadaver knees (eight knees, four male knees) with a mean age of 72 ± 7 years were used for tests involving a customized simulator capable of controlling quadriceps loading conditions. The muscle force distribution of the quadriceps for the normal loading condition was applied on the basis of muscle cross-sectional area data, as previously reported (VM: 31 N; RF/VI: 49 N; VL: 45 N). To simulate vastus medialis (VM) impairment, we set the muscle force for VM in the muscle force distribution of the quadriceps at zero (VM: 0 N; RF/VI: 49 N; VL: 45 N). The joint reaction forces and moments on knee joints that underwent total knee arthroplasty (TKA) did not differ significantly according to VM impairment status for all flexion angles (p > 0.05). Nevertheless, the vectors of internal–external moments mostly showed a tendency for alteration from external to internal due to VM impairment. This tendency was evident in 9 cases in 12 total test pairs (with and without VM impairment). Furthermore, the vectors of the anterior–posterior reaction forces mostly showed a tendency to increase anteriorly due to VM impairment. This tendency was also evident in 9 cases in 12 total test pairs (with and without VM impairment). These results indicate that posterior dislocation of the tibia may be induced if VM impairment occurs after TKA. In conclusion, VM impairment in knee joints undergoing TKA may contribute to posterior dislocation of the tibia by a paradoxical roll-back with enhancements of the anterior joint reaction force and external moment during knee-joint flexion. Our findings may be valuable for understanding the mechanism of potential instability and malfunction due to VM impairment in knee joints after TKA, and may help to optimize clinical/rehabilitation training plans to improve the prognosis (stability and function) of knee joints undergoing TKA.

Load-Sharing and Kinematics of the Human Cervical Spine Under Multi-Axial Transverse Shear Loading: Combined Experimental and Computational Investigation.

The cervical spine experiences shear forces during everyday activities and injurious events yet there is a paucity of biomechanical data characterizing the cervical spine under shear loading. This study aimed to (1) characterize load transmission paths and kinematics of the subaxial cervical spine under shear loading, and (2) assess a contemporary finite element cervical spine model using this data. Subaxial functional spinal units (FSUs) were subjected to anterior, posterior, and lateral shear forces (200 N) applied with and without superimposed axial compression preload (200 N) while monitoring spine kinematics. Load transmission paths were identified using strain gauges on the anterior vertebral body and lateral masses and a disc pressure sensor. Experimental conditions were simulated with cervical spine finite element model FSUs (GHBMC M50 version 5.0). The mean kinematics, vertebral strains, and disc pressures were compared to experimental results. The shear force-displacement response typically demonstrated a toe region followed by a linear response, with higher stiffness in anterior shear relative to lateral and posterior shear. Compressive axial preload decreased posterior and lateral shear stiffness and increased initial anterior shear stiffness. Load transmission patterns and kinematics suggest the facet joints play a key role in limiting anterior shear while the disc governs motion in posterior shear. The main cervical spine shear responses and trends are faithfully predicted by the GHBMC cervical spine model. These basic cervical spine biomechanics and the computational model can provide insight into mechanisms for facet dislocation in high severity impacts, and tissue distraction in low severity impacts.

Muscle volume imbalance may be associated with static posterior humeral head subluxation

BackgroundThe transverse force couple (TFC) of the rotator cuff (subscapularis vs. infraspinatus and teres minor muscle) is an important dynamic stabilizer of the shoulder joint in the anterior-posterior direction. In patients with posterior static subluxation of the humeral head (PSSH), decentration of the humeral head posteriorly occurs, which is associated with premature arthritis. We hypothesize that not only pathologic glenoid retroversion but also chronic muscle volume imbalance in the transverse force couple leads to PSSH.MethodsA retrospective analysis of the TFC muscle volumes of 9 patients with symptomatic, atraumatic PSSH, within 8 were treated with glenoid correction osteotomy, was conducted. The imaging data (CT) of 9 patients/10 shoulders of the full scapula and shoulder were analyzed, and the muscle volumes of the subscapularis (SSC), infraspinatus (ISP) and teres minor muscles (TMM) were measured by manually marking the muscle contours on transverse slices and calculating the volume from software. Furthermore, the glenoid retroversion and glenohumeral distance were measured.ResultsThe mean glenoid retroversion was − 16° (− 7° to − 31°). The observed mean glenohumeral distance was 4.0 mm (0 to 6.8 mm). Our study population showed a significant muscle volume imbalance between the subscapularis muscle and the infraspinatus and teres minor muscles (192 vs. 170 ml; p = 0.005). There was no significant correlation between the subscapularis muscle volume and the glenohumeral distance (r = 0.068), (p = 0.872).ConclusionThe muscle volume of the SSC in patients with PSSH was significantly higher than the muscle volume of the posterior force couple (ISP and TMM). This novel finding, albeit in a small series of patients, may support the theory that transverse force couple imbalance is associated with PSSH.Level of evidenceLevel 4 – Case series with no comparison group.

The Medial structures of the knee have a significant contribution to posteromedial rotational laxity control in the PCL-deficient knee.

Various reconstruction techniques have been employed to restore normal kinematics to PCL-deficient knees; however, studies show that failure rates are still high. Damage to secondary ligamentous stabilizers of the joint, which commonly occurs concurrently with PCL injuries, may contribute to these failures. The main objective of this study was to quantify the biomechanical contributions of the deep medial collateral ligament (dMCL) and posterior oblique ligament (POL) in stabilizing the PCL-deficient knee, using a joint motion simulator. Eight cadaveric knees underwent biomechanical analysis of posteromedial stability and rotatory laxity using an AMTI VIVO joint motion simulator. Combined posterior force (100N) and internal torque (5Nm) loads, followed by pure internal/external torques (± 5Nm), were applied at 0, 30, 60 and 90° of flexion. The specimens were tested in the intact state, followed by sequential sectioning of the PCL, dMCL, POL and sMCL. The order of sectioning of the dMCL and POL was randomized, providing n = 4 for each cutting sequence. Changes in posteromedial displacements and rotatory laxities were measured, as were the biomechanical contributions of the dMCL, POL and sMCL in resisting these loads in a PCL-deficient knee. Overall, it was observed that POL transection caused increased posteromedial displacements and internal rotations in extension, whereas dMCL transection had less of an effect in extension and more of an effect in flexion. Although statistically significant differences were identified during most loading scenarios, the increases in posteromedial displacements and rotatory laxity due to transection of the POL or dMCL were usually small. However, when internal torque was applied to the PCL-deficient knee, the combined torque contributions of the dMCL and POL towards resisting rotation was similar to that of the sMCL. The dMCL and POL are both important secondary stabilizers to posteromedial translation in the PCL-deficient knee, with alternating roles depending on flexion angle. Thus, in a PCL-deficient knee, concomitant injuries to either the POL or dMCL should be addressed with the aim of reducing the risk of PCL reconstruction failure.

Design and validation of an automated dual-arm instrumented intravaginal dynamometer.

(1) To present the design of a novel intravaginal dynamometer (IVD) capable of measuring vaginal closure force on both the anterior and posterior arms, (2) to use bench testing to validate the force, speed of arm opening, and positional accuracy of load measurement along the IVD arms, and (3) to present in vivo force measurements made with this device, comparing forces measured by the anterior and posterior arms. IVD load measurements were validated against an Instron® Universal Tester, arm opening speeds were validated using video analysis, and position-load accuracy was validated against calibration weights. In vivo IVD data were acquired from female volunteers during passive opening and pelvic floor muscle contraction tasks. Anterior and posterior IVD arm force outcomes were compared. Forces measured by the IVD and Instron® exhibited a strong linear relationship with excellent model fit. The speed control system was valid when tested under physiological loading conditions, however smaller antero-posterior opening diameters (25 and 30 mm) exhibited some error. The loading position along the IVD arms had no effect on force outcomes. In vivo data exhibited differences between force outcomes measured at the anterior and posterior aspects of the vagina during active contraction and passive elongation of the pelvic floor muscles. This IVD design demonstrates valid load measurement and speed control during bench testing. Active and passive forces measured are consistent with the literature. With dual instrumented arms, this device allows for further investigation into the source of measured vaginal closure forces.

Evaluation and management of elbow injuries in the adolescent overhead athlete.

With an increased interest in youth sports, the burden of overhead throwing elbow injuries accompanying early single-sport focus has steadily risen. During the overhead throwing motion, valgus torque can reach and surpass Newton meters (N m) during the late cocking and early acceleration phases, which exceeds the tensile strength (22.7–33 N m) of the ulnar collateral ligament. While the ulnar collateral ligament serves as the primary valgus stabilizer between and degrees of elbow flexion, other structures about the elbow must contribute to stability during throwing. Depending on an athlete’s stage of skeletal maturity, certain patterns of injury are observed with mechanical failures resulting from increased medial laxity, lateral-sided compression, and posterior extension shearing forces. Together, these injury patterns represent a wide range of conditions that arise from valgus extension overload. The purpose of this article is to review common pathologies observed in the adolescent overhead throwing athlete in the context of functional anatomy, osseous development, and throwing mechanics. Operative and non-operative management and their associated outcomes will be discussed for these injuries.

Is load control necessary to produce physiological AP displacement and axial rotation in wear testing of TAR?

The International Standard Organization, ISO 22622, specifies two options for joint wear simulator evaluation of total ankle replacements (TARs): load-controlled and displacement-controlled. In the present study, the load-controlled testing parameters were applied to cadaveric specimens to quantify and compare the observed sagittal translations and axial rotations to those specified under the displacement-controlled option. Twelve cadaveric specimens were stripped of extraneous tissues, keeping surrounding ankle ligaments. A halo was used to produce plantarflexion and dorsiflexion of the talus through two screws, while a baseplate resisted axial loads. The axial force and torque were applied to the tibia and fibula under force and torque feedback control. An anterior-posterior force was applied to the tibia. Plantarflexion-dorsiflexion were applied using rotation control. To protect the cadaveric specimens, loads were applied at 50% of the specified load profile while plantarflexion-dorsiflexion rotation was applied as specified. There was variation among specimens in magnitudes of anterior-posterior displacement with peaks ranging from 3.3 mm posteriorly to 3.0 mm anteriorly. Likewise, there was variation among specimens in magnitude of axial rotation, with peaks ranging from 11° external rotation to 4.5° internal rotation. However, the mean magnitudes of AP displacement and axial rotation did not exceed those specified by ISO 22622.

Functional muscle synergies to support the knee against moment specific loads while weight bearing

ObjectiveExternally applied abduction and rotational loads are major contributors to the knee joint injury mechanism; yet, how muscles work together to stabilize the knee against these loads remains unclear. Our study sought to evaluate lower limb functional muscle synergies in healthy young adults such that muscle activation can be directly related to internal knee joint moments. MethodsConcatenated non-negative matrix factorization extracted muscle and moment synergies of 22 participants from electromyographic signals and joint moments elicited during a weight-bearing force matching protocol. ResultsTwo synergy sets were extracted: Set 1 included four synergies, each corresponding to a general anterior, posterior, medial, or lateral force direction. Frontal and transverse moments were coupled during medial and lateral force directions. Set 2 included six synergies, each corresponding to a moment type (extension/flexion, ab/adduction, internal/external rotation). Hamstrings and quadriceps dominated synergies associated with respective flexion and extension moments while quadriceps-hamstring co-activation was associated with knee abduction. Rotation moments were associated with notable contributions from hamstrings, quadriceps, gastrocnemius, and hip ab/adductors, corresponding to a general co-activation muscle synergy. ConclusionOur results highlight the importance of muscular co-activation of all muscles crossing the knee to support it during injury-inducing loading conditions such as externally applied knee abduction and rotation. Functional muscle synergies can provide new insight into the relationship between neuromuscular control and knee joint stability by directly associating biomechanical variables to muscle activation.

Effects of an elastic resistance band exercise program on kinetics and muscle activities during walking in young adults with genu valgus: A double-blinded randomized controlled trial

BackgroundThis double-blinded randomized-controlled-trial aimed to identify the effects of an elastic band resistance training on walking kinetics and muscle activities in young adults with genu valgus. MethodsForty-two male young adults aged 22.5(2.7) years with genu valgus were randomly allocated to two experimental groups. The intervention group (n = 21) conducted a 14-weeks elastic band resistance training. The control group was passive during the intervention period and received the same treatment after the post-tests. Pre and post training, ground reaction forces and lower limb muscle activities were recorded during walking. FindingsResults revealed significant group-by-time interactions for peak medial ground reaction force and time-to-peak for posterior ground reaction force in favor of the intervention group (p < 0.012; d = 0.83–3.76). Resistance training with elastic bands resulted in significantly larger peak medial ground reaction force (p < 0.001; d = 1.45) and longer time-to-peak for posterior ground reaction force (p < 0.001; d = 1.85). Finding showed significant group-by-time interactions for peak positive free moment amplitudes in favor of the intervention group (p < 0.001; d = 1.18–2.02). Resistance training resulted in a lower peak positive free moment amplitude (p = 0.001; d = 1.46). With regards to muscle activities, the analysis revealed significant group-by-time interactions for rectus femoris and gluteus medius activities during the push-off phase in favor of the intervention group (p < 0.038; d = 0.68–0.89). Resistance training induced higher rectus femoris (p = 0.038; d = 0.84) and gluteus medius (p = 0.007; d = 0.54) activities. InterpretationThis study proved the effectiveness of resistance training using elastic bands on kinetics and muscle activities during walking in male adults with genu valgus disorder. Given that this training regime is low cost, effective, and easy-to-administer, we suggest that it should be implemented as a rehabilitative or preventive means for young adults with genu valgus.

Biomechanical asymmetries persist after ACL reconstruction: results of a 2-year study

PurposeThis study was aimed to examine longitudinal (6, 12, 18, 24 months) asymmetries in double-leg landing kinetics and kinematics of subjects with and without unilateral ACLR.MethodsThree-dimensional kinematic and kinetic parameters of 40 participants (n = 20 post-ACLR, n = 20 healthy) were collected with a motion analysis system and force plate during a drop-landing task, and asymmetry indices were compared between groups.ResultsThe asymmetry index (AI) in the ACLR group compared to the healthy group decreased from six to 24 months for vertical ground reaction force (vGRF) from 100% to 6.5% and for anterior posterior ground reaction force (a-pGRF) from 155.5% to 7%. Also, the AI decreased for peak hip flexion moment from 74.5% to 17.1%, peak knee flexion moment from 79.0% to 5.8% and peak ankle dorsiflexion moment from 59.3% to 5.9%. As a further matter, the AI decreased for peak hip abduction moment from 67.8% to 5.1%, peak knee adduction moment from 55.7% to 14.8% and peak knee valgus angle from 48.7% to 23.5%.ConclusionsResults obtained from this longitudinal study showed that ACLR patients still suffer from limb asymmetries during landing tasks, which appear to normalize by 24-monthspost-surgery. This finding can help us to better understand biomechanics of the limbs after ACLR, and design more efficient post-surgery rehabilitation programs.Level of evidenceLevel III.

Effect of Foot-Planting Strategy on Anterior Cruciate Ligament Loading in Women During a Direction Diversion Maneuver: A Musculoskeletal Modeling Approach.

Background:Although there is a higher prevalence of noncontact anterior cruciate ligament (ACL) injuries during a direction diversion maneuver (DDM), no previous studies have reported how foot-planting strategies affect ACL loading.Purpose:To investigate the effect of foot-planting strategies on ACL loading in women during a DDM task using a musculoskeletal modeling approach.Study Design:Descriptive laboratory study.Methods:A total of 13 female participants performed a DDM task, which involved running at 4.5 ± 0.2 m/s and turning left at 35° to 55° under a foot-planting strategy in 3 directions: neutral, toe-in, and toe-out. Kinematic and kinetic data were measured with the use of a 3-dimensional motion capture system and force platform to calculate variables such as joint angle, shear force, and moment. Anterior ACL and posterior ACL forces were extracted using musculoskeletal modeling.Results:The peak anterior ACL force was significantly larger for the toe-out condition (31.29 ± 4.02 N/body weight [BW]) compared with the toe-in condition (25.43 ± 5.68 N/BW) (P = .047), with no significant difference in the neutral condition. The toe-out condition had a higher knee valgus angle (2.98° ± 4.20°; P = .041), knee shear force (10.20 ± 1.69 N/BW; P = .009), and knee internal rotation moment (–0.18 ± 0.16 N·m/BW×height; P = .012) than the toe-in and neutral conditions.Conclusion:Through musculoskeletal modeling, we were able to conclude that the toe-out condition during the DDM might result in a higher risk of ACL injuries. Athletes and sports practitioners should avoid the toe-out foot-planting strategy when participating in a sporting activity.Clinical Relevance:Based on these findings, medical professionals and athletic coaches can gain knowledge on how foot-planting strategy affects ACL loading. Understanding the actual cause of an ACL injury can be useful for designing preventive training programs or strategies to decrease the risk of such injuries.

Anterior-posterior ground reaction forces across a range of running speeds in unilateral transfemoral amputees

ABSTRACT As a fundamental motor pattern, the ability to run at a range of constant speeds is a prerequisite for participating in competitive games and recreational sports. However, it remains unclear how unilateral transfemoral amputees modulate anterior and posterior ground reaction force impulses (GRFIs) in order to maintain constant running speeds. The purpose of this study was to investigate anterior and posterior GRFIs across a wide range of constant running speeds in unilateral transfemoral amputees wearing a running-specific prosthesis. Eleven runners with unilateral transfemoral amputation ran on an instrumented treadmill at 5 different speeds (30%, 40%, 50%, 60%, and 70% of the average velocity of their 100-m personal records). Anterior-posterior ground reaction forces (GRFs) were measured at 1000 Hz over 14 consecutive steps. Impulse, magnitude, and duration of anterior and posterior GRFs were compared between the affected and unaffected limbs at each speed. The net anterior-posterior GRFI, reflecting the changes in horizontal running velocity, was consistently positive (propulsion) in the affected limb and negative (braking) in the unaffected limb at all speeds. Regardless of running speed, unilateral transfemoral amputees maintain constant running speeds not over each step, but over 2 consecutive steps (i.e., one stride).

Implant placement in the removable mandibular advancement device for completely edentulous patients: a finite element study

Abstract Few studies have examined the biomechanical effects of dental implant placement in the implant-supported mandibular advancement device (MAD) for the treatment of obstructive sleep apnea in completely edentulous patients. This biomechanical study aimed to evaluate the stability of the implant-supported MAD for different numbers and positions of dental implants. A 3D edentulous maxillofacial model with the one-piece MAD was considered for various numbers and positions of implants. On each mandible and maxilla, one, two, four, or six implants were placed symmetrically in various positions. Total 42 implant placements were considered. A static finite element analysis was performed under the mandibular posterior restorative force for 40% protrusion. The maximum and minimum principal stresses on the cortical and cancellous bones and the von Mises stresses on the implant were measured. When four implants were placed on each maxilla and mandible, the maximum average stress on the cancellous bone was reduced by up to approximately three times compared with the cases of placing two implants on each maxilla and mandible. The placement of at least four implants on each maxilla and mandible improved MAD stability. It is noteworthy that the mandibular implants should be arranged adjacently to avoid stress concentration in the second molar.

Understanding the mechanics of closure is key to optimal midurethral sling technique

The animal experiments and prototype midurethral sling operations demonstrated that the sling provided new collagen to reinforce weak pubourethral ligaments (PUL). The now strengthened PULs were able to restore the contractile power of the 3 oppositely-acting directional closure forces. By contraction, these three forces exponentially altered the intraurethral resistance to flow when they closed the urethra to sustain continence. Relaxation of the forward force allowed the two posterior forces to uninhibitedly open the posterior urethral wall just prior to detrusor contraction, to facilitate evacuation of urine. The aim of this work is to examine the mechanics of the component anatomical structures which contribute to these functions, to analyse how subtle details impact on the actual surgical technique of the midurethral sling operations to optimize success, contribute to complications and how to prevent and fix them.

BIOMECHANICAL EFFECTS OF HYPERPRONATION ON MULTIDIRECTIONAL ANKLE ANGULAR DISPLACEMENT AND STIFFNESS

Hyperpronation of the foot is believed to contribute to ankle hypermobility and associated stiffness reduction, but the underlying biomechanical mechanisms remain unknown. This study aimsed to investigate multidirectional ankle displacement and associated stiffness when a posterior–anterior impact force was applied to the posterior knee compartment. Forty healthy adults with and without foot hyperpronation were recruited. A three-dimensional motion capture system and force plates were used to acquire angular displacement and ankle joint moment data. The independent [Formula: see text]-test and Mann–Whitney [Formula: see text] test were used to compare the group differences in ankle angular displacement, moment, and stiffness. Spearman’s rho test was performed to determine the relationship between ankle angular displacement and stiffness. The hyperpronation group demonstrated significantly greater sagittal ([Formula: see text]) and frontal plane ([Formula: see text]) angular displacements and reduced sagittal plane ankle stiffness ([Formula: see text]) than the neutral group. The Spearman’s correlation analysis showed a close inverse relationship between the ankle angular displacement and stiffness, ranging from [Formula: see text] to [Formula: see text]. The biomechanical data in our study suggest that individuals with foot hyperpronation present with multidirectional hypermobility and a reduction in ankle stiffness. These factors contribute to an increased risk of ankle-foot injury in individuals with foot hyperpronation.

Ground Reaction Forces Are Predicted with Functional and Clinical Tests in Healthy Collegiate Students.

Increased vertical and posterior ground reaction forces (GRFs) are associated with anterior cruciate ligament (ACL) injury. If a practical means to predict these forces existed, ACL injury risk could be attenuated. Forty-two active college-age individuals (21 females, 20.66 ± 1.46 y, 70.70 ± 2.36 cm, 82.20 ± 7.60 kg; 21 males, 21.57 ± 1.28 y, 65.52 ± 1.87 cm, 64.19 ± 9.05 kg) participated in this controlled laboratory study. GRFs were ascertained by having the subjects perform a unilateral landing task onto a force plate. Several clinical measures (Fat Free Mass (FFM), dorsiflexion passive range of motion (DPROM), isometric peak force of the lateral hip rotators, knee flexor/extensor peak force ratio (H:Q), the completion of the overhead deep squat), two functional tests (Margaria–Kalamen, Single Leg Triple Hop (SLTH)), and sex served as the predictor variables. Regression models to predict the GRFs normalized to the FFM (nGRFz, nGRFy) were generated. nGRFz was best predicted with a linear regression equation that included SLTH and DPROM (adjusted R2 = 0.274; p = 0.001). nGRFy was best predicted with a linear regression equation that included H:Q, FFM, and DPROM (adjusted R2 = 0.476; p < 0.001). Simple clinical measures and functional tests explain a small to moderate amount of the variance associated with the FFM normalized vertical and posterior GRFs in active college-age individuals.

Arthroscopic Suture Fixation With Autograft Augmentation Reconstruction for Delayed Tibial Avulsion Fractures of the Posterior Cruciate Ligament.

Background:The optimal surgical treatment of delayed avulsion fractures of the posterior cruciate ligament (PCL) is still controversial.Purpose:To evaluate the clinical results of arthroscopic suture fixation of tibial avulsion fractures of the PCL with autograft augmentation reconstruction.Study Design:Case series; Level of evidence, 4.Methods:From January 2013 to February 2017, we treated 15 patients with delayed tibial avulsion fractures of the PCL arthroscopically through posteromedial and posterolateral portals. The PCL and avulsion bone fragment were fixed with No. 2 nonabsorbable FiberWire sutures that were pulled out through a single tibial bone tunnel and fixed on a small Endobutton. Concomitantly, anatomic PCL augmentation reconstruction was performed, and the graft was pulled out through the same tunnel and fixed with an interference screw. Knee stability was assessed using the posterior drawer test, and the side-to-side difference was determined using a KT-1000 arthrometer with 134 N of posterior force at 30° of knee flexion. The International Knee Documentation Committee (IKDC) 2000 subjective form and Lysholm scale were used to evaluate clinical outcomes at follow-up. Overall, 12 patients were enrolled for analysis. The mean follow-up period was 34.4 months (range, 26-49 months).Results:At the final follow-up, 2 patients encountered 10° terminal flexion limitations. All patients had negative posterior drawer test results. The KT-1000 arthrometer side-to-side difference was significantly decreased from 8.25 ± 1.96 mm preoperatively to 1.08 ± 0.86 mm at the last follow-up (P < .001). The mean IKDC and Lysholm scores, respectively, increased from 54.67 ± 7.13 and 53.50 ± 7.90 preoperatively to 91.13 ± 3.78 and 94.25 ± 3.32 at the final follow-up (P < .001 for both).Conclusion:Arthroscopic suture fixation with autograft augmentation reconstruction for delayed tibial avulsion fractures of the PCL showed good clinical stability and function in this study.

The Association of Mammography Environment and Image Quality.

This study sought to determine if a mammogram performed in a multi-sensory environmental upgraded room (UR) is associated with improved image quality when compared to a standard room (SR). A retrospective analysis (interrupted time series design) of compression force and posterior nipple line (PNL) measurements was performed on 303 women (mean age 60.9 years) who underwent screening mammography for 2 consecutive years (year 1 in SR, year 2 in UR) at a single outpatient facility. Using the Picture Archiving Communication System (PACS), craniocaudal (CC) and mediolateral oblique (MLO) images for the two years were reviewed. The PNL was measured for the CC and MLO images bilaterally using the embedded tools in the PACS software. Posterior nipple line and compression force were analyzed using a paired t-test. Bland-Altman plots were used to obtain 95% limits of agreement (LOA) between the UR and SR. Image quality as determined by PNL measurement distance was greater in the UR (P < 0.001) when compared with the SR, with similar compression force (P ≥ 0.14). Mean PNL measurement differences ranged from 5.0 to 6.2 mm greater in the UR, whereas mean compression force differences ranged from -2.4 to 1.5 newtons. The 95% LOA suggest that PNL measurement differences between the UR and SR can vary by -11.0 to 27.0 mm. Environmentally modifying mammography rooms may improve image quality with regard to PNL measurements without increasing compression force.

An Experimental Study on the Safety and Mechanism of Reduction of Subaxial Cervical Facet Dislocation Using Z-Shape Elevating-Pulling Reduction Technique

We sought to clarify the safety and unlocking mechanism of the Z-shape elevating-pulling closed reduction (ZR) technique and to analyze the differences in facet contact force and intraspinal pressure during subaxial facet dislocation reduction using the ZR technique and traditional skull traction closed reduction (SR). In 15 human cadaveric skull-neck-thorax specimens, reproducible unilateral and bilateral facet dislocations (UFDs/BFDs) were created at the C5-C6 level and then reduced by applying the ZR and SR techniques, respectively. Tekscan FlexiForce A-201 pressure sensors were used to measure the anterior and posterior intraspinal pressure and injured facet contact force under physiological conditions and before and after reduction. The maximum pressures during the reduction process were recorded. After creation of the facet dislocation, the anterior and posterior intraspinal pressure and facet contact force were significantly increased relative to normal (P < 0.001). The UFDs and BFDs of all specimens were successfully reduced by both ZR and SR, and the intraspinal pressure and facet contact force were significantly reduced compared with before reduction (P < 0.001). Compared with SR, the maximum posterior intraspinal pressure during BFD reduction (P= 0.027) and the maximum facet contact force during UFD reduction (P < 0.001) were lower when ZR was used for closed reduction. Our findings suggest that ZR and SR can both be used to reduce subaxial facet dislocation and decompress the spinal cord. However, the ZR technique appears to safer and more effective than the SR technique for closed reduction of subaxial facet dislocations.